Method for installation of a ceiling system

ABSTRACT

A method is for installing a ceiling system attached to a structural ceiling surface. The method includes illuminating, in sequence and by a projector, different subsets of a set of optical sensors separately arranged in a known distribution pattern on the structural ceiling surface. Each optical sensor of the set of optical sensors is arranged to output a temporal signal indicative of a level of illumination. The method also includes determining an image plane relative to the projector based on the known distribution pattern of the set of optical sensors and the outputted temporal signals of each of the optical sensors, and displaying, by the projector, an image indicative of installation locations of the ceiling system at the image plane.

FILED OF THE INVENTION

The present invention generally relates to a method for installation ofa ceiling system attached to a structural ceiling surface.

BACKGROUND OF THE INVENTION

A tile system in a room or in another accommodation may serve a varietyof purposes. One purpose of having a tile system such as a suspendedceiling system or ceiling system attached to a structural ceiling may beto conceal an underside of a space, such as another room, which islocated above the room. The tile system may hence be installed toimprove the visual appearance of a room.

Another purpose may be to provide improved noise absorption and/or noiseattenuation in and outside of the room by having a tile system includingacoustic elements. The tiles then typically are acoustic elements andmay comprise a mineral fibre material, such as glass wool.

A resulting plenum space located between a suspended ceiling and astructural ceiling of a room may further be utilized to accommodate e.g.wiring, piping, as well as devices related to heating, ventilation andair condition.

Moreover, acoustic elements may be used to improve the acousticalenvironment in a room while at the same time improve the visualappearance of the room.

The acoustic elements or tiles may be suspended form a surface in a roomor may be attached to a surface in a room.

Moreover, the mounting of the tile system or ceiling system must be veryprecise since even a slight misalignment of the ceiling system or anacoustic element may have a big visual impact on the aestheticalappearance of the ceiling.

When the elements of the tile system or ceiling system are installed atoblique angles with respect to each other, it becomes even moredifficult to precisely position and mount the elements of the ceilingsystem.

Thus, the positioning of the elements must be carefully measured. Thiswork typically involves cumbersome work performed on ladders orscaffoldings and is prone to errors.

In one kind of a typical ceiling installation, a group of acousticelements in form of tiles may by arranged in a grid of profiles. Theprofiles are typically attached to a surface in a room, such as astructural ceiling.

When installing acoustic elements, which are arranged in a grid ofprofiles, the installation process is time consuming and complex. Thegrid of profiles must be precisely attached to the surface of the roomor else the acoustic elements will not properly fit in the grid.

Moreover, the mounting of the grid of profiles must be very precisesince even a slight misalignment of the grid or an acoustic element mayhave a big visual impact on the aesthetical appearance of the ceiling.

When the profiles of the grid are installed at oblique angles withrespect to each other, it becomes even more difficult to preciselyposition and mount the profiles of the grid.

Thus, the positioning of the profiles must be carefully measured. Thiswork typically involves cumbersome work performed on ladders orscaffoldings and is prone to errors.

Moreover, when a tile system is installed over a large area, workersinstalling the tile system typically will have climb up and down ondifferent ladders or scaffoldings in order to be able to reach thecomplete area of installation. This work is even more cumbersome and mayput safety at risk.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention is toprovide an improved method for installation of a ceiling system attachedto a structural ceiling surface.

A further object is to provide such a method which is less complex andless prone to errors when installing a ceiling system.

It is also an object to provide a cost-effective method requiring lesstime and consequently less work labour for installing a ceiling system.

It is also an object to provide a more versatile method allowing agreater flexibility when it comes to installing a ceiling system.

To achieve at least one of the above objects and also other objects thatwill be evident from the following description, a method forinstallation of a ceiling system having the features defined in claim 1,is provided according to the present invention. Preferred embodimentswill be evident from the dependent claims.

More specifically, there is provided according to the present inventiona method for installation of a ceiling system attached to a structuralceiling surface, the method comprising; in sequence illuminating, by aprojector, different sub sets of a set of optical sensors separatelyarranged in a known distribution pattern on the structural ceilingsurface, wherein each optical sensor of the set of optical sensors beingarranged to output a temporal signal indicative of a level ofillumination, determining an image plane relative to the projector basedon the known distribution pattern of the set of optical sensors and theoutputted temporal signals of each of the optical sensors, anddisplaying, by the projector, an image indicative of installationlocations of the ceiling system at the image plane.

Hereby an improved method for installation of a ceiling system isprovided.

The method is for installation of a ceiling system attached to astructural ceiling surface.

The ceiling system may comprise a plurality of elements, such as ceilingtiles, absorber elements, acoustic elements, profiles or similar, so asto form a rectangular pattern. In other words, the plurality of elementsmay be arranged in a parallel manner.

The ceiling system may comprise a plurality of elements arranged atoblique angels with respect to each other so as to form an irregularpattern of elements. In other words, the plurality of elements may bearranged in a non-parallel manner. The method comprises, in sequenceilluminating, by a projector, different sub sets of a set of opticalsensors separately arranged in a known distribution pattern on thestructural ceiling surface.

A set of optical sensors is therefore arranged on the structural ceilingsurface. The sensors may be arranged directly on the structural ceilingsurface or may be arranged indirectly for instance by being provided ina sensor housing which in turn is attached to the structural ceilingsurface. The set of optical sensors are arranged in a known distributionpattern, meaning that the relative locations of the respective opticalsensors are known. In other words, the mutual distances and the mutualdirections of the respective optical sensors are known. The absolutelocations of the optical sensors with respect to a reference locationmay additionally be known.

Different subsets of the of a set of optical sensors are illuminated bya projector in sequence. Hence, different combinations of opticalsensors may be illuminated by a projector. A single optical sensor maybe included in more than one subset of optical sensors. Also, a singleoptical sensor may be regarded a subset. The different subsets areilluminated in sequence, meaning that the respective subsets areilluminated consecutively in time after each other.

Different illumination sequences may be employed by the projector toilluminate the optical sensors in sequence. In practice, an illuminationsequence may include a number of different illumination patternsemployed by the projector in sequence. Each illumination pattern maythen typically include a pattern of illuminated areas on the structuralceiling surface and consequently also include non-illuminated areas ofthe structural ceiling surface. The same subset may be illuminated morethan once when conducting the method.

Each optical sensor of the set of optical sensors is arranged to outputa temporal signal indicative of a level of illumination. Hence, eachoptical sensor is arranged to output a signal which varies in time withthe illumination level detected by the optical sensor in question. Thesignal may be an analogue signal, a digital signal or a combinationthereof. The signal level being outputted may be to scale with theillumination level detected by the optical sensor in question. Thesignal level being outputted may be subject to a mathematical transformapplied to the illumination level detected by the optical sensor inquestion. The signal level being outputted may be subject to a thresholdof the illumination level detected by the optical sensor in question,such that a signal is outputted or correspondingly interrupted when adetected illumination level exceeds a predetermined threshold value.

An image plane is determined relative to the projector based on theknown distribution pattern of the set of optical sensors and theoutputted temporal signals of each of the optical sensors. Byilluminating subsets of the optical sensors in sequence with a series ofknown illumination patterns, it may be determined for which illuminationpatterns or pattern a specific optical sensor is illuminated. That is, aspace angle range with respect to the projector may be established basedon the illumination pattern at hand, where the illumination patternincludes an illuminated portion or portions being projected over a knownspace angle range. Hence, the optical sensor in question will output atemporal signal indicative of how the optical sensor is beingilluminated during the illumination sequence. In a corresponding manner,all optical sensors will output a respective temporal signal indicativeof how the respective optical sensors are illuminated during theillumination sequence.

By combing the outputted temporal signals of each of the optical sensorswith the known distribution pattern an image plane relative to theprojector may be determined. The image plane may thus be determined bymathematical calculations. For example, the image plane relative theprojector may be determined using homography algorithms as is known inthe art. As is known, homography typically refer to the homographymatrix which is the transfer matrix of projective transforms. Thehomography matrix is a linear transformation from a 2D plane to another.In the present case homography inversion, i.e. inverting the homographymatrix, may advantageously be employed in determining the image plane.

After having determined the image plane relative to the projector basedon the known distribution pattern of the set of optical sensors and theoutputted temporal signals of each of the optical sensors, an imageindicative of installation locations of the ceiling system may bedisplayed by the projector at the determined image plane. In otherwords, the projector may display an image which is compensated so as tobe displayed in a desired manner at the image plane. Hence, the imagemay be displayed such that installation locations of the ceiling systemat the image plane are displayed in a desired manner corresponding toactual installation locations of the ceiling system at the image plane.This may be done by adjusting the input to the projector such that theimage is projected with a correct scale at the image plane.

The image may include simple indications of installation locations ofthe ceiling system. The image may visualise the complete installation ofthe ceiling system to be installed including indications of installationlocations of elements such as tiles or primary profiles. The image maythus visualise a complete installation of the ceiling system toinstalled including any tiles or absorber elements and indications ofinstallation locations of primary profiles. The image may includeadditional information.

Next, elements of the ceiling system are typically attached to thestructural ceiling surface in locations corresponding to theinstallation locations indicated in the displayed image. The elementsmay be attached directly to the structural ceiling surface or may besuspended below at a distance from the structural ceiling surface.

The ceiling system may comprise a grid of profiles comprising aplurality of primary profiles, and the act of displaying the image maycomprise displaying information indicative of installation locations ofthe primary profiles at the image plane.

The grid of profiles may comprise a plurality of profiles arranged so asto form a rectangular grid of profiles. In other words, the plurality ofprofiles may be arranged in a parallel manner. A rectangular grid ofprofiles typically includes a plurality of rectangular spaces foraccommodating ceiling tiles, absorber elements, acoustic elements orsimilar.

The grid of profiles may comprise a plurality of profiles arranged atoblique angels with respect to each other so as to form an irregulargrid of profiles. In other words, the plurality of profiles may bearranged in a non-parallel manner. An irregular grid of profilestypically includes a plurality of irregular spaces of different sizesand shapes for accommodating ceiling tiles, absorber elements, acousticelements or similar.

The individual profiles of the grid of profiles are typically straightprofiles. The individual profiles of the grid of profiles may have bentor curved shape. The profiles may be made of metal, plastic or any othersuitable sufficiently rigid material.

The grid of profiles typically comprises a plurality of primaryprofiles. The primary profiles typically extend in a non-interruptedmanner along an installation of a ceiling system. The primary profilesmay be formed of a plurality of detachable sections, jointly forming theprimary profiles.

The primary profiles may be attached directly to a structural ceilingsurface or may be suspended below at a distance from the structuralceiling surface as is known in the art.

The primary profiles are typically interconnected by cross runners orcross profiles. By utilizing cross runners interconnecting the pluralityof main runners the main runners may be stabilized and less prone to runin an undesired curved fashion.

Moreover there may be provided, a method for installation of a grid ofprofiles of a ceiling system attached to a structural ceiling surface,wherein the grid of profiles comprises a plurality of primary profiles,the method comprising; in sequence illuminating, by a projector,different sub sets of a set of optical sensors separately arranged in aknown distribution pattern on the structural ceiling surface, whereineach optical sensor of the set of optical sensors being arranged tooutput a temporal signal indicative of a level of illumination,determining an image plane relative to the projector based on the knowndistribution pattern of the set of optical sensors and the outputtedtemporal signals of each of the optical sensors, and displaying, by theprojector, an image indicative of installation locations of the primaryprofiles at the image plane.

Hereby an improved method for installation of a grid of profiles of aceiling system may be provided.

The act of determining the image plane may comprise determining theimage plane such that the image plane substantially includes physicallocations of the optical sensors of the set of optical sensors. Bydetermining the image plane such that the image plane substantiallyincludes physical locations of the optical sensors of the set of opticalsensors, the image plan may be determined such that it substantiallycoincides with the structural ceiling surface on which the set ofoptical sensors is arranged.

The act of displaying the image may comprise displaying the image on thestructural ceiling surface. Hence, the image displayed at the imageplane may thus be displayed at the structural ceiling surface in adesired manner such that installation locations of the ceiling system atstructural ceiling surface are displayed in a desired mannercorresponding to actual installation locations of the elements of theceiling system at the structural ceiling surface.

The act of displaying the image may comprise calculating a projectivetransform based on a location of the projector relative to the imageplane, and applying the projective transform to the image such that thedisplayed image is compensated for size and wrap with respect to thestructural ceiling surface. The image transform may be calculated usinga homography algorithm, as discussed above, and the image transform maythen be applied to the image such that the image is compensated for sizeand wrap with respect to the structural ceiling surface. Morespecifically, homography inversion, i.e. inverting the homographymatrix, may advantageously be employed in determining the projectivetransform.

In practice, the image transform may be applied to the image byadjusting the input to the projector accordingly. Hence, the projectormay display an image which is compensated for size and wrap with respectto the structural ceiling surface so as to display the image in adesired manner at the structural ceiling surface. Hence, the image maybe displayed such that installation locations of the elements of theceiling system at the image plane are displayed in a desired mannercorresponding to actual installation locations of the elements of theceiling system at the structural ceiling surface.

The act of determining the image plane may comprise determining arotation of the projector relative to a desired direction of theinstallation locations of the ceiling system at the image plane based onthe known distribution pattern of the set of optical sensors and theoutputted temporal signals of each of the optical sensors, and whereinthe act of displaying the image comprises compensating a rotation of theimage based on the determined rotation. The image rotation may becalculated using a homography algorithm and a rotation compensation maythen be applied to the image such that the image is compensated forrotation with respect to the structural ceiling surface. Morespecifically, homography inversion, i.e. inverting the homographymatrix, may advantageously be employed in determining the rotation ofthe projector relative to a desired direction of e.g. installationlocations of primary profiles at the image plane based.

In practice, the rotation compensation may be applied to the image byadjusting the input to the projector accordingly. Hence, the projectormay display an image which is compensated for size and wrap with respectto the structural ceiling surface so as to display the image in adesired manner at the structural ceiling surface. Hence, the image maybe displayed such that installation locations of the elements of theceiling system, such as primary profiles, at the image plane aredisplayed in a desired manner corresponding to actual installationlocations of the elements of the ceiling system at the structuralceiling surface.

The act of displaying the image may comprise adjusting a position of theimage at the image plane based on building information model data, BIMdata. By adjusting a position of the image at the image plane based onbuilding information model data, BIM data, the position of the image maybe adjusted such that the installation locations of the elements of theceiling system are aligned with certain building features, such as wallsor air outlets. Correspondingly, the position of the image may beadjusted such that installation locations of e.g. primary profiles arepositioned at locations where there is a reduced risk of interferingwith or damaging concealed features of the building, such as piping orelectrical cables.

The act of displaying the image may comprise adjusting a position of theimage at the image plane based on a user-initiated input signal, whichis advantageous in that a user may adjust the position of the image in asimple manner.

The optical sensors of the set of optical sensors may be arranged atlocations corresponding to junctions of the grid of profiles. Byarranging the optical sensors of the set of optical sensors at locationscorresponding to junctions of the grid of profiles, a person installingthe grid of profiles may get a visual confirmation that the image isdisplayed correctly. Hence, a person installing the grid of profiles mayeasily verify that the junctions of the grid of profiles are displayedat locations where the optical sensors are located at the structuralceiling surface. In this way, a person installing the grid of profilesmay also verify that the image plane has been correctly determined orelse the junctions of the grid of profiles may incorrectly be displayedat locations where the optical sensors are not located.

The optical sensors of the set of optical sensors may be arranged on acommon substrate which is adapted to be arranged at the structuralceiling surface. By arranging the optical sensors of the set of opticalsensors on a common substrate which is adapted to be arranged at thestructural ceiling surface, the distribution pattern of the set ofoptical sensors may be kept constant and fixed in a secure manner.Moreover, the distribution pattern of the set of optical sensors may notneed to be measured or considered by a person installing the ceilingsystem since the distribution pattern of the set of optical sensors maybe fixed by the common substrate. Hence, the mutual distances anddirections between the optical sensors of the set of optical sensors maybe fixed and thus well known. Also, the method may become more efficientsince a person installing the ceiling system may not have to spend timeon installing a plurality of individual optical sensors.

The act of displaying the image may comprise displaying installationguidance based on building information model data, BIM data, which isadvantageous in that installation guidance may be displayed while takingfeatures of the building into account.

The act of displaying the image may comprise displaying fix points ofthe ceiling system to be installed, which is advantageous in that fixpoints may be displayed at locations where there is a reduced risk ofinterfering with or damaging concealed features of the building, such aspiping or electrical cables. Hence, a person installing the ceilingsystem may get a visual guidance regarding where to safely fix theelements of the ceiling system.

The act of displaying the image may comprise displaying forbidden areasfor fix points of the ceiling system to be installed, which isadvantageous in that areas where fix points would risk interfering withor damaging concealed features of the building, such as piping orelectrical cables, may be highlighted to a person installing the ceilingsystem. Hence, a person installing the ceiling system may get a visualguidance regarding where to not fix the elements of the ceiling system.

The act of displaying the image may comprise displaying fix points ofprimary profiles to be installed, which is advantageous in that fixpoints may be displayed at locations where there is a reduced risk ofinterfering with or damaging concealed features of the building, such aspiping or electrical cables. Hence, a person installing the grid ofprofiles may get a visual guidance regarding where to safely fix thegrid of profiles.

The act of displaying the image may comprise displaying forbidden areasfor fix points of primary profiles to be installed, which isadvantageous in that areas where fix points would risk interfering withor damaging concealed features of the building, such as piping orelectrical cables, may be highlighted to a person installing the grid ofprofiles. Hence, a person installing the grid of profiles may get avisual guidance regarding where to not fix the grid of profiles.

The act of displaying the image may further comprise displaying buildinginformation model data, BIM data, which is advantageous in thatconcealed features of the building, such as piping or electrical cables,may be displayed to a person installing the ceiling system. Also,features of the building, such as piping or electrical cables, that hasnot yet been installed may be displayed to a person installing theceiling system. In this way a person installing the ceiling system mayaccount for features to be installed and hence save enough room for thefeatures to be installed.

The act of in sequence illuminating different sub sets of the set ofoptical sensors may comprise; in sequence illuminating different subsets of the set of optical sensors according to a first predetermineddichotomy pattern along a first major direction, and in sequenceilluminating different sub sets of the set of optical sensors accordingto a second predetermined dichotomy pattern along a second majordirection, the first major direction being perpendicular to the secondmajor direction, which is advantageous in that the an accurate spaceangle range or space angle for each optical sensor with respect to theprojector may be determined. In other words, the direction along whichimaginary beam of the projector each optical sensor is located may bedetermined. By illuminating different sub sets of the set of opticalsensors according along a first major direction and a second majordirection, where the first major direction being perpendicular to thesecond major direction, the space angle range or space angle for eachoptical sensor with respect to the projector may be determined in seriesfor the first major direction and the second major directionrespectively.

The method may further comprise, arranging a second projector, separatefrom the projector, at a distance from the structural ceiling surface,and displaying, by the projector and the second projector, the imageindicative of installation locations of the ceiling system at the imageplane. By utilizing a projector and a second projector to jointlydisplay the image indicative of installation locations of the ceilingsystem, such as elements and primary profiles, at the image plane,several advantages are achieved. For instance, an increased display areaor installation area may be covered. Further, an increased redundancymay be achieved in case of failure of the projector or the secondprojector. Furthermore, the risk of certain areas of the image planebeing shadowed, by for instance pillars, light armatures, inner walls orsimilar, may be reduced.

Further features of, and advantages with, the present inventive conceptwill become apparent when studying the appended claims and the followingdescription. The skilled person will realize that different features ofthe present inventive concept may be combined to create variants otherthan those described in the following, without departing from the scopeof the present inventive concept.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects of the inventive concept, including its particular featuresand advantages, will be readily understood from the following detaileddescription and the accompanying drawings, in which:

FIG. 1 conceptually illustrates a room in which a ceiling systemincluding a grid of profiles is to be installed using a method forinstallation of a ceiling system.

FIG. 2 conceptually illustrates the room of FIG. 1 with a differentsensor setup as compared to FIG. 1 .

FIGS. 3 a-3 i schematically illustrates an illumination sequence andtemporal signals form two different sensors.

FIG. 4 conceptually illustrates the room of FIG. 1 at a later stage ofthe method where installation locations of primary profiles of the gridof profiles are displayed at a structural ceiling surface.

FIG. 5 conceptually illustrates the room of FIG. 1 while displayingadditional information on a structural ceiling surface.

FIG. 6 conceptually illustrates the room of FIG. 1 while using a secondprojector in addition to the projector.

FIG. 7 is a flowchart of a method for installation of a ceiling systemattached to a structural ceiling surface.

DETAILED DESCRIPTION

The present inventive concept will now be described more fullyhereinafter with reference to the accompanying drawings, in whichpreferred variants of the inventive concept are shown and discussed.This inventive concept may, however, be embodied in many different formsand should not be construed as limited to the variants set forth herein;rather, these variants are provided for thoroughness and completeness,and fully convey the scope of the inventive concept to the skilledperson. Like reference numerals refer to like elements throughout thedescription.

As have been described above, the present inventive concept generallyrelates to installation of ceiling systems attached to structuralceiling surfaces. Hence, installations of any type of ceiling systemsare encompassed by the present inventive concept. In the followingdescription, the present inventive concept it will be described inconjunction with ceiling systems including a grid of profiles. However,the present inventive concept is equally applicable for with ceilingsystems void of any grid of profiles.

FIG. 1 conceptually illustrates a room 100 in which a grid of profilesis to be installed using a method for installation of a grid of profilesof a ceiling system. A number of components used for executing themethod will be described below in conjunction with describing themethod. The method will be described sequentially below, and variantsthereof will be discussed in-line. The components used for executing themethod will sometimes be collectively referred to as a system.

More specifically, a grid of profiles of a ceiling system is to beattached to the structural ceiling surface 102 of the room 100. The gridof profiles to be installed comprises a plurality of primary profiles.The primary profiles are typically extending in a non-interrupted manneralong an installation of a ceiling system. The method described forinstallation of a grid of profiles of a ceiling system includesdisplaying an image indicative of installation locations of the primaryprofiles. Primary profiles are thereafter typically attached to thestructural ceiling surface 102 in locations corresponding to theinstallation locations indicated in the displayed image.

In the room 100 there is provided a projector 104. The projector 104forming part of the system used for executing the method. The projector104 is arranged on the floor 106 of the room 100. The projector 104 mayalternatively be arranged on a wall or at the ceiling of the room 100.The projector 104 may be of any suitable kind. Examples of suitableprojectors 104 include SD, HD and 4K video projectors or beamers.Projectors 104 capable of displaying colour images are preferred whileprojectors 104 capable of displaying black and white images ormonochromic images will suffice. Also, a laser projector 104 may be usedto advantage. The projector 104 is connected to an image source 108. Theimage source 108 may be any device capable of providing an image signalto the projector 104. Examples of suitable image sources includes,computers, laptops, tablets and media players such an Apple TV® to givea few non-limiting examples. The image source 108 may be connected tothe projector 104 by a wired connection, a wireless connection or acombination thereof. In the depicted system, the image source 108 isconnected by wired connection to the projector 104.

The image source 108 includes a processor 108 a capable of processingand altering image data. The processor 108 a is typically capable ofprocessing an incoming image signal in order to feed out an image signalsuitable for the projector 104 in question. Alternatively, oradditionally, the image source 108 may include a memory 108 b havingstored thereon image data used to produce an image signal for suitablefor the projector 104 in question. The processor 108 a may alter ormanipulate the image data so as to alter or manipulate the imagedisplayed by the projector 104.

The image source 108 is preferably attached to the projector 104 so asto form a single unit. The image source 108 may be integral to theprojector 104. The image source 108 may be separate the projector 104.

The depicted system used for executing the method further includes auser device 110. The user device 110 may be connected to the imagesource 108 by a wired connection, a wireless connection or a combinationthereof. The depicted user device 110 is a handheld device which isconnected to the image source 108 by a wireless connection. The userdevice 110 may be any suitable device such as computers, laptops, mediaplayers and tablets such as an iPad® to give a few non-limitingexamples. The user device 110 is arranged to transmit an image signal tothe image source 108 or to transmit data relevant for the image source108 to produce an image signal for the projector 104. The user device istypically capable of receiving different types of input form a user. Theinput may be input related to image adjustment, image manipulation,sensor locations, mutual distances, mutual directions, brightness,contrast, amount of image information, etc.

The user device 110 and the image source 108 may be the same device.

The depicted system used for executing the method further includes a setof optical sensors including four optical sensors 112 a-d. The opticalsensors 112 a-d are arranged on the structural ceiling surface 102 ofthe room 100. More specifically, the optical sensors 112 a-d arearranged on a common substrate 114. Hence, the optical sensors 112 a-dare arranged indirectly on the structural ceiling surface 102 of theroom 100. The common substrate 114 is adapted to be arranged on thestructural ceiling surface 102. The common substrate 114 may for examplebe a board of thin material, a plate or similar. The common substrate114 may be foldable and may for that purpose include hinges, fold linesor similar. By the common substrate 114 the optical sensors 112 a-d areseparately arranged in a known distribution pattern on the commonsubstrate 114 and hence on the structural ceiling surface 102. In otherwords, the mutual distances and mutual directions between the respectiveoptical sensors 112 a-d are fixed by the common substrate 114 and hencethe distribution pattern in known. The common substrate 114 is held atthe structural ceiling surface 102 by means of a holder 116 in form ofan adjustable tripod.

In FIG. 1 four optical sensors 112 a-d are depicted. However, moreoptical sensors may be used, such as 5, 7, 10 or 50 optical sensors. Byusing more optical sensors, an increased accuracy may be achieved.However, in the following a system having four optical sensors 112 a-dwill be described.

Each of the four optical sensors 112 a-d are connected to the userdevice 110 by means of a wireless connection. Each optical sensor 112a-d of the set of optical sensors being arranged to output a temporalsignal indicative of a level of illumination. In other words, eachoptical sensor 112 a-d is arranged to output a time sequential signalwhich is dependent on a level of illumination impinging on the opticalsensor 112 a-112 d in question. The temporal signal indicative of alevel of illumination will be discussed in greater detail below whenreferring to FIG. 3 .

As an alternative, each optical sensor 112 a-d of the set of opticalsensors may be attached by a respective wired connection to a commonwireless transmitter. The wireless transmitter may in turn be connectedto the user device 110 by means of a wireless connection. The wirelesstransmitter may in this case advantageously be arranged on the commonsubstrate 114.

As a further alternative, each optical sensor 112 a-d of the set ofoptical sensors may be attached by a respective wired connection to acommon wireless transmitter. The wireless transmitter may in turn beconnected to the projector 104 by means of a wireless connection. Thewireless transmitter may in this case advantageously be arranged on thecommon substrate 114.

As can be seen in FIG. 1 , the projector 104 illuminates a portion 118of the structural ceiling surface 102 of the room 100. The depictedilluminated portion 118 covers a major portion of the structural ceilingsurface 102 of the room 100. As depicted in FIG. 1 , the illuminatedportion 118 of the structural ceiling surface 102 includes a bright area118 a with high illumination intensity and a less bright area 118 b witha lower illumination intensity. The optical sensors 112 a and 112 c arepresent in the bright area 118 a with high illumination intensitywhereas the sensors 112 b and 112 d are present in the less bright area118 b with a lower illumination intensity. Hence, in the depicted momentof FIG. 1 , optical sensors 112 a and 112 c will output a respectivesignal indicative of a higher level of illumination as compared tooptical sensors 112 b and 112 d. Signals outputted by the opticalsensors 112 a-112 d will be discussed in greater detail below whenreferring to FIG. 3 .

Now referring to FIG. 2 , here room 100 is depicted with a differentsetup of optical sensors 212 a-212 d. In order to avoid unduerepetition, only differences in relation to FIG. 1 will be discussedbelow.

The optical sensors 212-a-d are arranged on the structural ceilingsurface 102 of the room 100. More specifically, the optical sensors 212a-d are arranged directly on the structural ceiling surface 102 of theroom 100. The respective optical sensors 212 a-d may for instance beglued to or screwed to the structural ceiling surface 102 of the room100. The optical sensors 212 a-d are separately arranged on thestructural ceiling surface 103. In other words, the mutual distances anddirections between the respective optical sensors 212 a-d are fixed bythe optical sensors 212 a-d being arranged on the structural ceilingsurface 103. However, in this case, the distribution pattern will notdirectly be known per se. This means that a user executing the methodwill have to carefully determine the mutual distances and directionsbetween the respective optical sensors 112 a-d after the optical sensors212 a-d have been arranged on the structural ceiling surface 103, or theuser executing the method will have to carefully arrange the opticalsensors 212 a-d on the structural ceiling surface 102 according to apredetermined known distribution pattern. Hence, the distributionpattern of the optical sensors 212 a-d may be known either frommeasurements of the actual locations or from the fact that the opticalsensors 212 a-d are mounted according to a known distribution pattern.

The optical sensors 212 a-d are connected to the projector 104 byrespective wired connections. The projector 104 of FIG. 2 includes auser deice 110 and an image source 108 integrally formed with theprojector 104. The user device 110 and an image source 108 fulfilcorresponding purposes of those described in conjunction with FIG. 1 andwill not be described in greater detail here.

Now referring to FIGS. 3 a-3 i . According to the method, different subsets of the set of optical sensors 112 a-112 d (or 212 a-d) areilluminated in sequence by the projector 104.

In FIGS. 3 a-3 i it is schematically depicted how two optical sensorsdenoted S1, S2, corresponding to any of the optical sensors 112 a-112 d(or 212 a-d), are illuminated in sequence by the projector 104. If FIG.3 a-3 i two sensors S1, S2 are depicted for reasons of simplicity. Thesame principle does however apply to the situation where more opticalsensors are used. In FIG. 3 a-3 i , different subsets of the opticalsensors S1 and S2 are illuminated in sequence by an illuminationsequence including six different illumination patterns as depicted inFIGS. 3 a-3 f . The different subsets are corresponding to the actualoptical sensors S1, S2 being illuminated at a certain point in time.

In the following, FIGS. 3 a-3 i will be referred to as schemes a-i,where schema a refers to FIG. 3 a , scheme b to FIG. 3 b etc. All sixschemes a-f shows the same area of a structural ceiling surface 102 onwhich the two optical sensors S1 and S2 are arranged. The respectiveschemes a-f shows the same area of the structural ceiling surface 102 atdifferent points in time where scheme a corresponds to a first point intime and scheme f corresponds to a last point in time of the respectiveschemes. The sequential illumination of the optical sensors S1, S2according to the illumination sequence including six differentillumination patterns is performed. The six different illuminationpatterns will result in that each of the optical sensors S1, S2 outputsa temporal signal TS1, TS2 indicative of a level of illumination at therespective schemes a-f. The temporal signals TS1 and TS2 are depicted inthe respective graphs g and h in FIG. 3 .

The outputted temporal signals TS1 and TS2 may in practice be used todetermine in which directions the optical sensors S1, S2 are arranged inrelation to the projector 104. In practice, a space angle interval withrespect to the projector may be determined for each optical sensor S1,S2. The space angle interval will in practice correspond an angleinterval along a first major direction and an angle interval along asecond major direction. The space angel intervals of the optical sensorsS1, S2 will thus correspond to a respective area A1, A2 at thestructural ceiling surface 102. This is illustrated in scheme i in FIG.3 .

In the following it will be described in greater detail how therespective directions to sensors S1, S2 are determined by illuminatingdifferent subsets of the sensors S1, S2 in sequence by the projector104.

Before the first illumination of scheme a is employed a dark levelsignal with the projector tuned off is preferably recorded as areference signal.

In the first illumination pattern of scheme a, sensor S1 is illuminatedwhile sensor S2 is not. In other words, sensor S1 is at scheme a locatedin an area with high illumination intensity while sensor S2 is locatedin an area with a lower illumination intensity such as a backgroundillumination intensity. At the point in time corresponding to scheme a,sensor S1 will output a signal indicative of a higher level ofillumination as compared to sensor S2. This is illustrated in schemes gand h where it may be seen that the temporal signal TS1 of sensor S1 hasa higher signal level than the temporal signal TS2 of sensor S2 at pointa. In fact, the temporal signal TS2 of sensor S2 is set to a zero sincecorresponding to a background illumination level.

Form the respective temporal signals TS1, TS2 and the illuminationpattern at scheme a, it may be concluded that sensor S1 is locatedsomewhere in the area indicated by the bracket above scheme a.Correspondingly, it may be concluded that sensor S2 is located somewherein the area indicated by the bracket below scheme a. This because sensorS1 is in the illuminated area at the right of scheme a, while sensor S2is in the non-illuminated area at the left of scheme a.

Followingly, the sensors S1, S2 are illuminated with a secondillumination pattern of scheme b. Sensors S1 and S2 are not illuminatedwhen the second illumination pattern scheme b is employed. In otherwords, both sensor S1 and sensor S2 are located in an area with a lowillumination intensity such as a background illumination intensity. Atthe point in time corresponding to scheme b, sensors S1 and S2 willoutput signals indicative of a low level of illumination. This isillustrated in schemes g and h where it may be seen that the temporalsignals TS1 and TS2 both have a low signal level at point b.

Form the respective temporal signals TS1, TS2 and the illuminationpattern at scheme b, it may be now be concluded that sensor S1 islocated somewhere in the area indicated by the bracket above scheme b.Correspondingly, it may be concluded that sensor S2 is located somewherein the area indicated by the bracket below scheme b.

Followingly, sensors S1, S2 are illuminated with a third illuminationpattern of scheme c. Sensors S1 and S2 are illuminated when the thirdillumination pattern of scheme c is employed. In other words, bothsensor S1 and sensor S2 are located in an area which is illuminated bythe projector 104. At the point in time corresponding to scheme c,sensors S1 and S2 will output signals indicative of a high level ofillumination. This is illustrated in schemes g and h where it may beseen that the temporal signals TS1 and TS2 both have a high signal levelat point c.

Form the respective temporal signals TS1, TS2 and the illuminationpattern at scheme c, it may be now be concluded that sensor S1 islocated somewhere in the area indicated by the bracket above scheme c.Correspondingly, it may be concluded that sensor S2 is located somewherein the area indicated by the bracket below scheme c.

The three initial illumination patterns are more specificallypredetermined dichotomy patterns along a first major direction.

Followingly, a fourth illumination pattern of scheme d is employed. Whenemploying the illumination pattern of scheme d sensor S1 is illuminatedwhile sensor S2 is not. In other words, sensor S1 is at scheme d locatedin an area with high illumination intensity while sensor S2 is locatedin an area with a lower illumination intensity such as a backgroundillumination intensity. At the point in time corresponding to scheme d,sensor S1 will output a signal indicative of a higher level ofillumination as compared to sensor S2. This is illustrated in schemes gand h where it may be seen that the temporal signal TS1 of sensor S1 hasa higher signal level than the temporal signal TS2 of sensor S2 at pointd.

Form the respective temporal signals TS1, TS2 and the illuminationpattern at scheme d, it may be concluded that sensor S1 is locatedsomewhere in the area indicated by the bracket to the right of scheme d.Correspondingly, it may be concluded that sensor S2 is located somewherein the area indicated by the bracket to the left of scheme d.

Followingly, the sensors S1, S2 are illuminated with a fifthillumination pattern of scheme e. Sensors S1 and S2 are not illuminatedwhen the fifth illumination pattern scheme e is employed. In otherwords, both sensor S1 and sensor S2 are located in an area with a lowillumination intensity such as a background illumination intensity. Atthe point in time corresponding to scheme e, sensors S1 and S2 willoutput signals indicative of a low level of illumination. This isillustrated in schemes g and h where it may be seen that the temporalsignals TS1 and TS2 both have a low signal level at point e.

Form the respective temporal signals TS1, TS2 and the illuminationpattern at scheme e, it may now be concluded that sensor S1 is locatedsomewhere in the area indicated by the bracket to the right of scheme e.Correspondingly, it may be concluded that sensor S2 is located somewherein the area indicated by the bracket to the left of scheme e.

Followingly, sensors S1, S2 are illuminated with a sixth illuminationpattern of scheme f. Sensors S1 and S2 are illuminated when the sixthillumination pattern of scheme f is employed. In other words, bothsensor S1 and sensor S2 are located in an area which is illuminated bythe projector 104. At the point in time corresponding to scheme f,sensors S1 and S2 will output signals indicative of a high level ofillumination. This is illustrated in schemes g and h where it may beseen that the temporal signals TS1 and TS2 both have a high signal levelat point f.

Form the respective temporal signals TS1, TS2 and the illuminationpattern at scheme f, it may be now be concluded that sensor S1 islocated somewhere in the area indicated by the bracket to the right ofscheme f. Correspondingly, it may be concluded that sensor S2 is locatedsomewhere in the area indicated by the bracket to the left of scheme f.

The three final illumination patterns of schemes d-f are morespecifically predetermined dichotomy patterns along a second majordirection, where the first major direction being perpendicular to thesecond major direction.

It may be concluded from the temporal signal TS1 of the six abovedescribed illumination patterns that the sensor S1 is located in thearea A1 of scheme i. Correspondingly, it may be concluded from thetemporal signal TS2 of the six above described illumination patternsthat the sensor S2 is located in the area A2 of scheme i. In practice,as described above the respective areas A1 and A2 of scheme icorresponds to in which directions the sensors S1, S2 are arranged inrelation to the projector 104. In practice, the number of illuminationpatterns of the above type may be increased so as to more accuratedetermine the locations of the sensors S1 and S2. In other words, byincreasing the number of illumination patterns of the above type theareas A1 and A2 of scheme i may be reduced in size.

As an alternative to predetermined dichotomy patterns, a relativelynarrow light cone may scan the structural ceiling surface 102 on whichthe optical sensors S1 and S2 are attached. It may be then be recordedfor what space angle the light cone impinges on the respective sensorsS1 and S2.

As an alternative to predetermined dichotomy patterns, a laser beam mayscan the structural ceiling surface 102 on which the optical sensors S1and S2 are attached. It may be then be recorded for what directions thelaser beam impinges on the respective sensors S1 and S2.

Other strategies may also be used to advantage for locating the opticalsensors S1 and S2 attached to the structural ceiling surface 102.

Now referring back also to FIG. 1 and FIG. 2 , as previously indicated,sensor S1 and sensor S2 may correspond to any of the optical sensors 112a-112 d of FIG. 1 or the optical sensors 212 a-f of FIG. 2 . Hence, in amanner corresponding to what has been described above in conjunction toFIG. 3 it may be concluded how the respective optical sensors 112 a-112d (or 212 a-d) are located relative to the projector 104 in terms of inwhich directions the sensors 112 a-112 d (or 212 a-d) are arranged inrelation to the projector 104.

Based on determined directions of the respective sensors 112 a-112 d (or212 a-d) and the known distribution pattern an image plane relative tothe projector may be now be determined by mathematical calculations.Needless to say, the directions of the respective sensors 112 a-112 d(or 212 a-d) need not be determined. Rather, an image plane relative tothe projector 104 may be determined based on the known distributionpattern of the set of optical sensors 112 a-112 d (or 212 a-d) and theoutputted temporal signals TS1, TS2 of each of the optical sensors 112a-112 d (or 212 a-d).

The image plane relative to the projector 104 may be determined usinghomography algorithms as is known in the art. The main purpose ofdetermining the image plane relative to the projector 104 is to correctthe image projected by the projector 104 to fit the plane of thestructural ceiling surface 102 or to at least compensate the imageprojected by the projector 104 to become parallel with the plane of thestructural ceiling surface 102.

The image plane relative to the projector 104 may be determined byinverting the homography matrix. In the subject case, the homographymatrix includes elements relating to positions of at least four opticalsensors 112 a-112 d (or 212 a-d).

For instance, the optical sensors 112 a-112 d may as depicted in FIG. 1be positioned at equivalent distances around a centre point. Hence, inFIG. 1 the intersection of the adjustable holder 116 and the commonsubstrate 114 may correspond to the centre point. The centre point mayfor reasons of simplicity is given the coordinates (0, 0), i.e. thecentre point may be considered to be located at the origin of acoordinate system having an X-axis and a Y-axis. The respective opticalsensors 112 a-112 d may for reasons of simplicity be given thecoordinates (1, 1), (−1, 1), (1, −1) and (−1, −1). That is, each opticalsensor may be considered located one distance or length unit away fromthe centre point in each one of the X-direction and the Y-direction. Alloptical sensors 112 a-112 d depicted in FIG. 1 are located in differentdirections with respect to the centre point which is reflected in thesigns of the respective coordinates of the optical sensors 112 a-112 d.

Hence, using the outputted temporal signals TS1, TS2 of each of theoptical sensors 112 a-112 d, the position of each optical sensor of theoptical sensors 112 a-112 d in view of the projector 104 may bedetermined. The positions of each of the optical sensors 112 a-112 d inthe view of the projector may be denoted coordinates (X₁, Y₁), (X₂, Y₂),(X₃, Y₃) and (X₄, Y₄).

Now considering the eight points (1, 1), (−1, 1), (1, −1), (−1, −1),(X₁, Y₁), (X₂, Y₂), (X₃, Y₃) and (X₄, Y₄) which may be included in a 3×3homography matrix.

The homography matrix including the eight points may now be inverted inorder to determine the image plane relative to the projector 104.

More specifically, the inverted homography matrix will result in atransform matrix or projective transform which when applied, to e.g. animage, will place the point (X₁, Y₁) in the point (1, 1), the point (X₂,Y₂) in the point (−1, 1), the point (X₃, Y₃) in the point (1, −1) andthe point (X₄, Y₄) in the point (−1, −1). The projective transform willconsequently include translation, rotation and scale.

The inversion of the homography matrix may for instance be calculatedusing the tool OpenCV which is a programming library mainly aimed atcomputer vison.

Since a projective transform have 8 degrees of freedom the locations ofat least four optical sensors 112 a-112 d (or 212 a-d) need to bedetermined in relation to the projector 104. The projective transformhas 8 degrees of freedom for 9 coefficients (3×3 matrix). However,because such transforms are defined within a scaling factor, whichremoves one degree of freedom, one of the coefficients can bearbitrarily set to 1.

After having determined the image plane relative to the projector 104,the projector may display an image indicative of installation locations120 of primary profiles at the image plane, as is shown in FIG. 4 .

More specifically, the user device 110 may determine the image planerelative to the projector 104 based on the known distribution pattern ofthe set of optical sensors 112 a-112 d (or 212 a-d) and the outputtedtemporal signals TS1, TS2 of each of the optical sensors 112 a-112 d (or212 a-d). This may typically be determined by mathematical calculationsperformed in the user device 110, e.g. according to the above example.The user device 110 may thus transmit a signal to the image source 108.The signal may thus be constituted such that the displayed image of theprojector 104 based on the image signal form the image source 108 isdisplayed at the determined image plane.

In FIG. 4 , it is illustrated how an image 122 is displayed at thestructural ceiling surface 102 of the room 100. Hence, the structuralceiling surface 102 corresponds to the determined image plane. The image122 includes installation locations 120 of primary profiles of the gridof profiles. In FIG. 4 it is depicted how installation locations 120 offive primary profiles are indicated as straight parallel lines displayedon the structural ceiling surface 102 of the room 100.

The optical sensors 112 a-d have been removed in FIG. 4 but may verywell be present at the time of displaying the image 122.

The displayed image 122 comprises displayed fix points 124 of theprimary profiles to be installed. The fixpoints 124 may be indicatedwith image features such as dots or crosses at locations where it isappropriate to fix the primary profiles to be installed. The displayedfixpoints 124 may consequently be displayed at certain distances where afirm installation of the primary profiles will be achieved while notusing an excessive amount of fix points 124.

Hence, in the situation depicted in FIG. 4 the image plane has beendetermined such that the image plane substantially includes physicallocations of the optical sensors 112 a-112 d (or 212 a-d) of the set ofoptical sensors. Moreover, the image 122 displayed by the projector 104is displayed on the structural ceiling surface 102. For this reason, aprojective transform has been calculated based on a location of theprojector 104 relative to the image plane. The projective transform mayadvantageously be calculated by the user device 110. The projectivetransform has been applied to the displayed image 122 depicted in FIG. 4. By applying the projective transform the displayed image 122 may becompensated for size and wrap with respect to the image plane andconsequently to the structural ceiling surface 102 of the room 100. Inother words, the projective transform may be applied such that the image122 is correctly displayed on the structural ceiling surface 102, i.e.the displayed image 122 indicative of installation locations 120 of theprimary profiles corresponds to actual and desired installationlocations of the primary profiles to be installed.

More specifically, the projective transform may be determined byinverting the homography matrix as described above.

Also, the rotation of the projector 104 relative to a desired directionof the installation locations 120 of primary profiles at the image planemay be determined. The rotation may be determined by mathematicalcalculations based on the known distribution pattern of the set ofoptical sensors 112 a-112 c (or 212 a-d) and the outputted temporalsignals TS1, TS2 of each of the optical sensors 112 a-112 c (or 212a-d). The rotation may be calculated by the user device 110 and mayconsequently be transmitted to the image source 108 such that therotation of the displayed image 122 is compensated based on thedetermined rotation.

More specifically, the rotation of the projector 104 relative to adesired direction of the installation locations 120 of primary profilesat the image plane may be determined from the projective transformresulting from inversion of the homography matrix as described above.

The position of the displayed image 122 of FIG. 4 may be adjusted basedon building information model data, BIM data. By adjusting the positionof the displayed image 122 based on BIM data the image 122 including theinstallation locations 120 of primary profiles at the image plane, i.e.at the structural ceiling surface 102, may be adjusted sideways suchthat the installation locations 120 of primary profiles at the imageplane are aligned with certain building features, such as walls or airoutlets. Correspondingly, the position of the image 122 may be adjustedsuch that installation locations 120 of the primary profiles arepositioned at locations where there is a reduced risk of interferingwith or damaging concealed features of the building, such as piping orelectrical cables. In order to achieve this, the user device 110 mayinclude BIM data stored therein or the user device 110 may receive BIMdata from a remote resource such as a server or a cloud service. Theuser device 110, may thus based on the BIM data adjust the signaltransmitted to the image source 108 such that the position of thedisplayed image 122 is adjusted sideways as desired.

The position of the displayed image 122 of FIG. 4 may be adjusted basedon a user-initiated input signal. Hence, a user may typically adjust theposition of the displayed image 122 by an input on the user device 110.The user device 110 may in response to the user input adjust the signaltransmitted to the image source 108 such that the position of thedisplayed image 122 including the installation locations 120 of primaryprofiles at the image plane, i.e. at the structural ceiling surface 102,is adjusted sideways as desired. By doing this, a user may adjust theposition of the mage 122 such that installation locations 120 of primaryprofiles at the image plane are aligned with certain building features,such as walls or air outlets. Correspondingly, the position of the image122 may be adjusted such that installation locations 120 of the primaryprofiles are positioned at locations where there is a reduced risk ofinterfering with or damaging concealed features of the building, such aspiping or electrical cables.

Correspondingly, a rotation of the displayed image 122 of FIG. 4 may beadjusted based on a user-initiated input signal.

The optical sensors 112 a-112 c (or 212 a-d) may be arranged atlocations corresponding to junctions of the grid of profiles to beinstalled. By this, a user may get an instant and visual confirmationthat the image 122 is displayed correctly, i.e. a user may verify thatthe sensors 112 a-112 c (or 212 a-d) actually are aligned at locationscorresponding to junctions of the grid of profiles in the displayedimage 122.

Now referring to FIG. 5 , here room 100 is depicted with a differentimage 222 displayed at the structural ceiling surface 102. In order toavoid undue repetition, only differences in relation to FIG. 4 will bediscussed below.

As can be seen in FIG. 5 , installation locations 220 of primaryprofiles to be installed are shown in the image 222. The installationlocations 220 of the of primary profiles to be installed are shown asstraight lines extending at oblique angles with respect to each other.Hence, the installation locations 220 of the of primary profiles to beinstalled are shown as non-parallel lines in the image 222.

The image 222 includes more information as compared to the image 122 ofFIG. 4 . The depicted image 222 of FIG. 5 includes installation guidance126 based on BIM data. The installation guidance 126 is thus displayedas a part of the image 222. The included installation guidance 126 isbased on BIM data in the sense that the displayed installation guidance126 is displayed in manner where features of the building is taken intoaccount. The displayed installation guidance 126 may for instance takeconcealed features of the building into account. Not yet installedfeatures of the building may be taken into account such that sufficientspace is left for the features to be installed later on. The displayedinstallation guidance 126 may thus be positioned in areas which aresuitable for installation of the primary profiles to be installed.

The displayed image 122 may include may include fix points 128 ofprimary profiles to be installed. The fix points 128 may thus bedisplayed at suitable locations where there is a reduced risk ofinterfering with or damaging concealed features of the building. Thefixpoints 128 may be indicated with image features such as dots orcrosses at locations where it is appropriate to fix the primary profilesto be installed. The displayed fixpoints 128 may consequently bedisplayed at certain distances where a firm installation of the primaryprofiles will be achieved while not using an excessive amount of fixpoints 128. The displayed fix points 128 is an example of displayedinstallation guidance 126.

The displayed image 122 may include forbidden areas 130 for fix points128 of primary profiles to be installed. The forbidden areas 130 may bedisplayed in areas where fix points 128 would risk interfering with ordamaging concealed features of the building, such as piping orelectrical cables. The forbidden areas 130 may be displayed in areaswhere fix points 128 would risk interfering with features of thebuilding that has not yet been installed. The displayed forbidden areas130 is an example of displayed installation guidance 126.

The displayed image 122 may include building information model data, BIMdata 132. The displayed image 122 may consequently visualise concealedfeatures 132 of the building, such as piping or electrical cables. Thedisplayed image 122 may consequently visualise features 132 of thebuilding that has not yet been installed. The image 122 may as a fewnon-limiting examples include visual representations 132 of cables,pipes, wires, airducts, air outlets, lighting appliances, heaters, smokedetectors, fans, wi-fi access points, sprinklers, interior walls andwindows.

The displayed installation guidance 126 may as a further example includea movie clip 134 showing an installation scheme how a typical primaryprofile is installed at the structural ceiling 102 of the room 100. Themovie clip 134, may include indications on where to fix the primaryprofiles to be installed. That is the movie clip 134 may includeinformation regarding fix points 128 of the primary profiles to beinstalled. The movie clip 134 may also include information regardingsuitable ways of drilling in the structural ceiling 102, as well aswhich type of fasteners to suitably use for the structural ceiling 102at hand. Hence, different drilling techniques and fasteners may bedisplayed based on the material of the structural ceiling 102 at hand.Information regarding the material of the structural ceiling 102 at handmay for instance be gathered by the user device 110 form a server havingBIM data stored thereon.

Now referring to FIG. 6 , here room 100 is depicted with two differentprojectors 104, 204 used to display an image 322 at the structuralceiling surface 102. In order to avoid undue repetition, onlydifferences in relation to FIG. 4 will be discussed below.

As is illustrated in FIG. 6 , a second projector 204 is arranged on thefloor 106 of the room 100 in addition to the projector 104. The secondprojector 204 is like the projector 104 arranged at a distance from thestructural ceiling surface 102. The image 322 is displayed at the imageplane by the projector 104 and the second projector 204. The image 322is jointly formed by the projector 104 and the second projector 204. Theimage source 108 connected to the projector and the image source 208connected to the second projector 204 are both connected to the userdevice 110. The user device 110 may thus distribute image data to theimage source 108 and the image source 208 such that the image 322 isjointly formed by the projector 104 and the second projector 204.Before, the image 322 may be displayed by the projector 104 and thesecond projector 204, a common image plane is determined for each one ofthe projector 104 and the second projector 204 as described above.

In the depicted setup of FIG. 6 , the image plane coincides with thestructural ceiling surface 102. Hence, the image 322 is displayed at thestructural ceiling surface 102. The image 322 includes installationlocations 120 of primary profiles. The installation locations 120 aredepicted as straight lines extending in parallel. However, differentlayouts of the installation locations 120 may be used to advantage whenusing a second projector 204 in addition to the projector 104. Also,information of the kind described in conjunction with FIG. 5 may bedisplayed in image 322. By utilising the projector 104 and the secondprojector 204 a larger installation area may be covered by the image 322at the same time. Moreover, an increased redundancy may be achieved incase of failure of the projector 104 or the second projector 204.Furthermore, the risk of certain areas of the structural ceiling surface102 being shadowed, by for instance pillars, light armatures, innerwalls or similar, may also be reduced.

Now referring to FIG. 7 in addition to FIGS. 1-6 . In FIG. 7 is shown aflow scheme of a method 700 which may be used for installation of a gridof profiles of a ceiling system attached to a structural ceiling surface102 as have been described above in conjunction with FIGS. 1-6 . Themethod 700 comprising; in sequence illuminating 702, by a projector 104,different sub sets of a set of optical sensors 112 a-d, 212 a-d, S1, S2separately arranged in a known distribution pattern on the structuralceiling surface 102, wherein each optical sensor 112 a-c, 212 a-c, S1,S2 of the set of optical sensors being arranged to output a temporalsignal TS1, TS2 indicative of a level of illumination, determining 704an image plane relative to the projector 104 based on the knowndistribution pattern of the set of optical sensors 112 a-c, 212 a-c, S1,S2 and the outputted temporal signals TS1, TS2 of each of the opticalsensors 112 a-d, 212 a-d, S1, S2, displaying 706, by the projector 104,an image 122, 222, 322 indicative of installation locations 120, 220 ofthe primary profiles at the image plane.

As is understood, the respective features and elements described inconjunction with the respective FIGS. 1-7 may be combined orinterchanged to suit specific installation needs, when installing a gridof profiles for a ceiling system.

Moreover, it will be appreciated that the concept of displaying an imageindicative of installation locations at an image plane mayadvantageously be used in the course of installing other entities thanprimary profiles of a grid of profiles for a ceiling system.

For instance, installation locations of ceiling tiles installedindependently, i.e. without a grid of profiles, may be displayed toadvantage a determined image plane.

Moreover, installation locations of sound absorbing baffles, such asceiling or wall mounted baffles may advantageously be displayed adetermined image plane.

Also, installation locations of other devices, such as fans, lightings,loudspeakers, sprinklers, wi-fi transceivers and air inlets may bedisplayed to advantage at a determined image plane.

It will be appreciated that the present inventive concept is not limitedto the variants shown. Several modifications and variations are thusconceivable within the scope of the invention which thus is exclusivelydefined by the appended claims.

1-18. (canceled)
 19. A method for installation of a ceiling systemattached to a structural ceiling surface, the method comprising:illuminating, in sequence and by a projector, different subsets of a setof optical sensors separately arranged in a known distribution patternon the structural ceiling surface, wherein each optical sensor of theset of optical sensors being arranged to output a temporal signalindicative of a level of illumination, determining an image planerelative to the projector based on the known distribution pattern of theset of optical sensors and the outputted temporal signals of each of theoptical sensors, and displaying, by the projector, an image indicativeof installation locations of the ceiling system at the image plane. 20.The method according to claim 19, wherein the ceiling system comprises agrid of profiles comprising a plurality of primary profiles, and whereinthe displaying the image comprises displaying information indicative ofinstallation locations of the primary profiles at the image plane. 21.The method according to claim 19, wherein the determining the imageplane comprises determining the image plane such that the image planesubstantially includes physical locations of the optical sensors of theset of optical sensors.
 22. The method according to claim 19, whereinthe displaying the image comprises displaying the image on thestructural ceiling surface.
 23. The method according to claim 22,wherein the displaying the image comprises calculating a projectivetransform based on a location of the projector relative to the imageplane, and applying the projective transform to the image such that thedisplayed image is compensated for size and wrap with respect to thestructural ceiling surface.
 24. The method according to claim 19,wherein the determining the image plane comprises determining a rotationof the projector relative to a desired direction of the installationlocations of the ceiling system at the image plane based on the knowndistribution pattern of the set of optical sensors and the outputtedtemporal signals of each of the optical sensors, and wherein thedisplaying the image comprises compensating a rotation of the imagebased on the determined rotation.
 25. The method according to claim 19,wherein the displaying the image comprises adjusting a position of theimage at the image plane based on building information model data, BIMdata.
 26. The method according to claim 19, wherein the displaying theimage comprises adjusting a position of the image at the image planebased on a user-initiated input signal.
 27. The method according toclaim 20, wherein the optical sensors of the set of optical sensors arearranged at locations corresponding to junctions of the grid ofprofiles.
 28. The method according to claim 19, wherein the opticalsensors of the set of optical sensors are arranged on a common substratewhich is adapted to be arranged at the structural ceiling surface. 29.The method according to claim 19, wherein the displaying the imagecomprises displaying installation guidance based on building informationmodel data, BIM data.
 30. The method according to claim 29, wherein thedisplaying the image comprises displaying fix points of the ceilingsystem to be installed.
 31. The method according to claim 29, whereinthe displaying the image comprises displaying forbidden areas for fixpoints of the ceiling system to be installed.
 32. The method accordingto claim 29, wherein the displaying the image comprises displaying fixpoints of primary profiles to be installed.
 33. The method according toclaim 29, wherein the displaying the image comprises displayingforbidden areas for fix points of primary profiles to be installed. 34.The method according to claim 19, wherein the displaying the imagefurther comprises displaying building information model data, BIM data.35. The method according to claim 19, wherein the illuminating differentsubsets of the set of optical sensors comprises: illuminating, insequence, different subsets of the set of optical sensors according to afirst predetermined dichotomy pattern along a first major direction, andilluminating, in sequence, different subsets of the set of opticalsensors according to a second predetermined dichotomy pattern along asecond major direction, the first major direction being perpendicular tothe second major direction.
 36. The method according to claim 19,further comprising: arranging a second projector, separate from theprojector, at a distance from the structural ceiling surface, anddisplaying, by the projector and the second projector, the imageindicative of installation locations of the ceiling system at the imageplane.